Masayori Furudate

Qualitative and quantitative evaluation of renal parenchymal damage by99mTc-DMSA planar and SPECT scintigraphy

The initial99mTc-DMSA studies carried out over a four year period in 229 patients with various heterogenic causes of lower urinary tract abnormalities were reviewed. Anatomical damage to the renal parenchyma was graded by means of planar and SPECT studies into a six group classification proposed by Monsour et al.: grade 0 (normal), I (equivocal), II (single defect), III (more than 2 defects), IV (contracted or small) and V (no visualization). Parenchymal uptake of99mTc-DMSA was quantitated from planar images at 2 hours postinjection by a computer assisted gamma camera method. SPECT studies could enhance the pick-up rate for parenchymal uptake defects by a factor of 1.5 in comparison with planar imaging. The incidence of anatomical damage to the renal parenchyma increased with a high radiological grade for VUR, and renal uptake per injection dose of99mTc-DMSA by the individual kidney significantly decreased in grades III and IV of the anatomical classification.These data revealed that99mTc-DMSA planar is still useful for evaluating gross structural damage and for quantitative evaluation of the kidney with computer assistance. SPECT scintigraphy is more effective in disclosing anatomical damage to the renal parenchyma than planar, although it needs further discussion as to whether SPECT may increase sensitivity with minimal or no adverse affect on specificity.

Single photon emission computed tomography with Tc-99m- dimercaptosuccinic acid in patients with upper urinary tract infection and/or vesicoureteral reflux

By means of Tc-99m dimercaptosuccinic acid (DMSA) scintigraphy, an established method for assessing renal cortical damage, we evaluated the pick-up rate for renal defects (scars) by single photon computed tomography (SPECT) and planar images of 10 normal volunteers, and 58 patients (70 scintigrams) with upper urinary tract infections, most of whom had a history of vesicoureteral reflux (VUR). The positive study rate for renal defects depended on the severity of VUR. The overall positive rates for renal cortical defects obtained by DMSA SPECT imaging and DMSA planar imaging were 60% and 43%, respectively, and the difference between these was significant (p < 0.005). The mean absolute individual renal uptake (/injected dose) at 2 hours post-injection was decreased in kidneys with defects detected by SPECT alone. The positive study rate for intravenous urography (IVU) depended on the grade of VUR and was 15 % overall.DMSA SPECT imaging detects renal cortical defects at greater frequency than previously achieved.

The use of three-phase bone imaging in vascularized fibular and iliac bone grafts

Three–phase bone imaging was undertaken to monitor the viability of vascularized bone grafts after surgery. Eleven vascularized fibular grafts and six vascularized iliac grafts were reviewed. The study evaluated patients over multiple time intervals from 1 week to 6–8 weeks postoperatively. Follow–up ranged from 12 to 60 months. In most of the patients who achieved a successful clinical outcome, the study was positive; blood perfusion and blood pool radioactivity at sites of bone grafts were higher than those at recipient sites two weeks postoperatively and became equal to surrounding tissue thereafter. The grafted bone uptake of radiophosphate was constantly positive in these cases. Conversely, the study was negative in three cases of postoperative vascular complications. Serial three–phase bone imaging is a useful tool to monitor the viability and early complications of vascularized bone grafts after surgery.

The role of201Tl scintigraphy in evaluating proliferative activity in thyroid neoplasms

To identify the relationship between the uptake of201Tl and the proliferative activity in thyroid neoplasms,201Tl scintigraphy was performed in 57 patients with thyroid neoplasms.201Tl uptake ratio was calculated in both the early and the delayed images and then compared with factors representing cellular or practical proliferative activity of the lesions. The labeling index (LI) for proliferating cell nuclear antigen (PCNA) was determined quantitatively by flow cytometry. There was a significant correlation between the uptake ratio and LI for PCNA. The correlation coefficient for the delayed ratio (DR) vs. LI was better than that for the early ratio (ER) vs. LI. As parameters for practical proliferation, the surgical stage in primary thyroid carcinoma or131I uptake in recurrent thyroid carcinoma was focused on. DR was strongly related to these parameters, regardless of the histopathological features or size of the lesions. Our results suggest that201Tl uptake in delayed thyroid scan is useful in assessing proliferative activity in thyroid neoplasms.

Captopril renoscintigraphy with Tc-99m DTPA in patients with suspected renovascular hypertension: prospective and retrospective evaluation

Sensitivity and specificity of captopril renoscintigraphy (CRS) with Tc-99m DTPA has been analyzed in 41 cases, 16 with renovascular hypertension (RVH) and 25 with non-RVH. The sensitivity and specificity of the baseline study were 63% (10/16) and 63% (12/19), respectively, based on the split renal function study in which the lower limit of normal was assumed to be 42% of the total renal uptake. Captopril renoscintigraphy yielded 67% (12/18) sensitivity and 76% (19/25) specificity. The low specificity of CRS was due to the application of a prospective criterion of the captopril-induced reduction rate (CRR) of less than −20%, which was calculated from the renal uptake before and after captopril. When criteria of CRR less than −25% were used, the specificity of CRS was improved to 96%, but the sensitivity declined to 61%. Changes in the configuration of the renogram induced by captopril also had high specificity but low sensitivity. Renovascular hypertension was most likely when criteria for both CRR and the renogram were fulfilled. These criteria often were diagnostic in patients with bilateral renal artery stenosis that showed variable scintigraphic responses to captopril challenge. Captopril renoscintigraphy is a very specific means to evaluate RVH, but may have limitations in certain clinical situations such as poorly preserved function of the affected kidney, prior long-term administration of captopril, prior surgical manipulation of stenotic renal artery, and chronic renal parenchymal damage.

Single photon emission computed tomography using201Tl chloride in pulmonary nodules: Comparison with67Ga citrate and99mTc-labeled hexamethyl-propyleneamine-oxime

A single photon emission computed tomography (SPECT) with201Tl chloride (Tl-201) was carried out prospectively in 50 patients with pulmonary nodules and its diagnostic value was compared with those of67Ga citrate (Ga-67) and99mTc-labeled hexamethyl-propyleneamineoxime (Tc-99m-HMPAO). Tl-201 SPECT provided 88% (early)–91% (delayed) sensitivity, 85% (early and delayed) specificity and 87% (early)–89% (delayed) accuracy. The sensitivity of the Tl-201 planar image was 56 (early)–62% (delayed), which was significantly lower than that of SPECT. Delayed SPECT images at 2 hour postinjection were more preferable to disclose the malignant pulmonary nodule than early SPECT images at 15 minutes postinjection. The application of SPECT with Ga-67 failed to improve the sensitivity of planar imaging for malignant pulmonary nodules. Tc-99m-HMPAO was concentrated in 62% of 13 patients with malignant pulmonary nodules, which was slightly higher than Ga-67 in 54% of 28 patients. In an analysis of the histologic types of lung cancer, the sensitivity of Tl-201 was not significantly different in all types. On the other hand, Ga-67 was positive only in 25% of 12 patients with adenocarcinoma.A combination of SPECT and Tl-201 is the best choice among routine scintigraphic techniques for depicting malignant pulmonary nodules. The Tl-201 SPECT image may play a complementary role in the characterization of pulmonary nodules which are revealed on a plain radiograph and computed tomography.

Phase II study of Tc-99m MAG3 in patients with nephrourologic diseases

Tc-99m-labeled mercaptoacetyltriglycine (Tc-99m MAG3) is a recently introduced radioagent that is excreted by tubular function. The aim of this study was to test Tc-99m MAG3 as an imaging agent for renal scintigraphy and renal plasma flow measurement. Image quality was tested with four different administered doses of Tc-99m MAG3, 100 MBq, 200 MBq, 300 MBq and 400 MBq, in four patients each. All administered doses except 100 MBq were sufficient for visible inspection of the nephrogram and drainage images; however, an administered dose higher than 300 MBq was necessary to maintain the quality of the blood perfusion image. The blood clearance with Tc-99m MAG3 or I-131 orthoiodohippurate (I-131 OIH) was calculated within the same day by the single blood sampling method. The blood clearance with Tc-99m MAG3 was 1.2-fold lower than with I-131 OIH, but correlated well (OIH = 91.34 ± 0.932 MAG3, r = 0.953, P < 0.001). The blood clearance with Tc-99m MAG3 also correlated with the percentage of renal uptake estimated by the count-based gamma camera method at 1.5 to 2.5 minutes after injection (ERPF = -59.13% ± 16.87% uptake, r = 0.845, P < 0.01). The mean labeling yield of Tc-99m MAG3 was 97%. None of the patients complained of side effects from Tc-99m MAG3. Tc-99m MAG3 is concluded to have good properties as a tubular radioagent for dynamic renal scintigraphy and renal plasma flow measurement.

Tc-99m labeled tissue-type plasminogen activator: preparation, stability and preliminary imaging of thrombus-bearing rats.

Tissue-type plasminogen activator (t-PA) is a thrombolytic agent that directly binds to fibrin formed in clots. In terms of radiolabeling and nuclear imaging, t-PA has several advantages in Tc-99m labeling: it is stable in acidic solution at pH 3, which is suitable for labeling Tc-99m by a method of stannous reduction and blood disappearance after administration is rapid, which is desirable for imaging targets using short-lived radionuclides.Recombinant t-PA was labeled with Tc-99m by a method of stannous reduction without significant degradation of biochemical activity, over 95 % of which was retained after the labeling procedure. Labeling efficiency in paper chromatography was over 98 %. The moiety of hydrolyzed Tc-99m that was not eluted through the Sephadex column was estimated to be less than 10%. Tc-99m labeled t-PA, however, appeared to become unstable when diluted with normal saline. Nevertheless, inin vitro fibrin binding, Tc-99m labeled t-PA showed high affinity with fibrin: 80% of 100 ng/ml of Tc-99m t-PA bound to 10−5 mol of the fibrinogen. Preliminary animal studies also showed a concentration of Tc-99m labeled t-PA at fresh thrombi formed in the inferior vena cava.Tc-99m labeled t-PA appears to have potential for thrombus imaging and the preparation of an instant kit.

Diffuse visualization of bone marrow with I-123 IMP in a malignant melanoma

I-123 IMP scintigraphy was performed on a 59-year-old man with malignant melanoma. The images showed diffuse uptake in the bone marrow. These findings were more evident when using I-123 IMP than with Ga-67 citrate. I-123 IMP does not normally concentrate in the bone marrow. I-123 IMP scintigraphy may be more sensitive and specific in evaluating the bone marrow metastases from a malignant melanoma.

Autoradiographic analysis of [14C]deoxy-D-glucose in thyroid cancer xenografts: A comparative study with pathologic correlation

An experimental model of thyroid cancer was prepared for evaluating the accumulation of [14C]deoxy-D-glucose ([14C]DG) in thyroid cancer xenografts (AC2). A continuous cell line established from a biopsy specimen of a metastatic thyroid carcinoma possessed the ability to synthesize the cellular protein without increase in cell division after adding bovine TSHin vitro. The histological sections of the xenografts resected from the131I treated nude mice mainly consisted of structures showing follicular and trabecular growth. Immunohistochemically the cytoplasm of the tumor cells was positive for human thyroglobulin(hTg). These observations provide strong evidence that the AC2 cell originates in the thyroid follicular epithelium. By comparing autoradiographic accumulation patterns of [14C]DG and histopathological examinations, it was found that the uptake of [14C]DG was higher in the granulation tissues surrounding necrosis than in viable tumor cells of trabeculary growing and follicle forming tissues.It is suggested that the degree of [14C]DG content reflects not only tumor cell viability and proliferation but also the inflammatory and degenerative reaction accompanying tumor cell growth.